This patch removes our own implementation of ssh-agent and switches to
using the ssh-agent program provided by OpenSSH. We can't simply drop
the ssh-agent functionality from gnome-keyring, as it enables the
following:
* Automatic loading and unlocking of keys
* Prompting in the UI
Instead we wrap the ssh-agent program as a subprocess and augment
the protocol as we need.
Co-authored-by: Daiki Ueno <dueno@src.gnome.org>https://bugzilla.gnome.org/show_bug.cgi?id=775981